docs: def _dtype_array(self):
          """Return mask for discrete(0)/continuous(1) attributes and their indices. Return array of max/min diffs of attributes."""
          attrtype = []
          attrdiff = []
  
          for key in self._headers:
              if self.attr[key][0] == 'continuous':
                  attrtype.append(1)
              else:
                  attrtype.append(0)
              attrdiff.append(self.attr[key][3])
  
          attrtype = np.array(attrtype)
          cidx = np.where(attrtype == 1)[0]
          didx = np.where(attrtype == 0)[0]
  
          attrdiff = np.array(attrdiff)
  
          return attrdiff, cidx, didx